Making terminations should be high on the list of good examples for the meaning behind the statement "the devil is in the details.” This task may seem simple but mistakes here could cause hours of troubleshooting or other types of problems after continued hours of use and aging of the installation. Let’s explore, from a high level, what you must concern yourself with when terminating conductors. I think you may see that this task, which quite often is left to the most inexperienced on the job, may need closer attention.
There may not be an immediate cause and effect when it comes to terminations gone wrong, as some problems may take quite some time to manifest themselves. Take the problem in Figure 1 as an example. This picture shows the use of an incorrect lug on a Photovoltaic panel. The dissimilar metals have caused corrosion to occur over time. I am quite sure that when it was first installed it looked great, but time has revealed the problem. The following are some, not all, of identifiable problems that poor terminations can cause.
Heat: Loose connections due to not being torqued properly can introduce impedance that reacts with the current to cause heat. The heat only acts to further degrade the connection point. Excessive heat at a termination can damage equipment on either side of the termination whether it be the insulation of the conductor or the equipment to which the conductor is attached.
Oxidation: Aluminum quickly develops a layer of oxide when exposed to air. This oxidation is highly resistive. Proper plating is required or the use of other paste-type products applied on the termination.
Corrosion: Dissimilar metals can introduce corrosion as shown in Figure 1. This acts to introduce more impedance into the circuit and if this connection is your ground return path or an equipment grounding system, your path of least resistance can be com-promised and your grounding system is not quite as effective as you had hoped. Corrosion can occur in aluminum conductors due to galvanic action, which occurs if dissimilar metals are used in an electrolytic solution.
Thermal Linear Expansion Coefficient: The fractional change in length of a particular material, for each degree of temperature change, can cause loose connections, which could result in heating.
Creep: Creep is the continued deformation of material under stress.
Voltage (Over/Under): If a termination is not made correctly and the wire to the load or from the source does not make the connection needed, you may experience a reduced voltage or even an overvoltage. Your overvoltage condition is a good example of losing the neutral on the line side of a residential home’s main loadcenter. I have had seen a handful of examples of this on homes where the neutral from the utility either in the meter or even at the transformer caused an overvoltage in the home, damaging electronics.
Arcing: Arcing from phase to phase, phase to neutral, or even phase to ground can occur if bare conductors touch equipment or touch other bare conductors. Stripping the insulation from the conductor before termination and damaging the insulation during termination can introduce opportunities for arc faults to occur.
NEC Violation: There are many areas in the National Electrical Code that focus on termination points. When mistakes are made, an inspector just may be able to point out the problem and the NEC Section it violates.
Miss-Operation: Improper voltage, high impedance paths, and arcing and sparking as well as other effects of poor terminations may cause equipment to not operate as expected. Whether it be sensitive electronic equipment, industrial control equipment, or a grounding system solution or more, mistakes in terminations may be a cause of miss-operation.
Violate UL Listing: If care is not taken in your terminations, you may be applying the product outside of its UL listing. Products are tested under certain conditions and test configurations. These are reflected in manufacturer instructions and can be found in the UL White Book. When a product is applied incorrectly, the safety of the application could be at risk as the configuration may have never been tested.
The above are just some of the ramifications that can be experienced when you do not make proper terminations. Some reading this article may have other great examples. I would encourage the sharing of these and more with your fellow workers to help raise the awareness of the importance of care in making terminations. Remember too that there are two ends to every conductor that will require to be terminated. Read instructions for the equipment to which terminations will be made. Your limiting factors may be on one of the two ends of the conductor you are terminating but will apply to both ends. Read equipment labels to which terminations will be made and understand the proper application of the conductor.
Codes and Standards
Codes and standards are there for safety. It is important that we understand these requirements. The following NEC sections are a great place to start:
Installation and Use: This is an important section as it is a reminder that listed or labeled equipment shall be installed and used in accordance with the instructions included in the listing or labeling. Set your instructions aside for review and don’t go dumpster diving for them after the job is done and problems arise.
Deteriorating Agents: This section focuses on the proper application of products, recognizing that external sources can have a deteriorating effect on conductors and/or equipment.
Mechanical execution of work: Neatness counts and in terminations it can make a world of difference. This section reminds us of our need to focus on tidy work. On any one job, terminations could be over-whelming in number. Neatness in work can help bring that level of clarity to your project so mistakes are not made.
Integrity of Electrical Equipment and Connections: Protection of key components in your equipment is important as terminating on lugs that have been contaminated with paint or other foreign materials could be a problem.
Electrical Connections: This section addresses dissimilar metals, fine stranded conductors, and necessary termination details and more. There is a section on terminals, splices, and temperature limitations. Materials such as solder, fluxes, and more are discussed as well.
There are many more sections in the Code that are important to effective terminations but the above can get you started. Knowing the Code and continuing studies as it changes will help in your effort in attention to the details.
Another important resource is the UL White Book and associated UL standards. The following categories can provide important information that will help in the understanding of how to apply products:
- AALZ: Electrical Equipment For Use in Ordinary Locations
- ZMOW: Wire-Connector Adapters
- ZMVV: Wire Connectors and Soldering Lugs
- ZMWQ: Sealed Wire-Connector Systems
The UL standards of most importance, in addition to individual product UL requirement documents, are shown below. Note that the white book is a free resource that contains all of the application information you need to know from the following standards:
- UL 486A – 486B: “Wire Connectors”
- UL 486A: “Wire Connectors and Soldering Lugs for Use With Copper Conductors”
- UL 486B: “Wire Connectors for Use with Aluminum Conductors”
- UL 486C: “Splicing Wiring Connectors”
- UL 486D: “Sealed Wire Connector Systems”
- UL 486E: “Equipment Wiring Terminals for Use with Aluminum and/or Copper Conductors”
The UL white book is a free download from the UL website.
Key Take Aways
Care should be taken when making terminations. Often, this work is left to the most inexperienced of the team. These individuals must understand how important their task at hand is and understand the code requirements that directly pertain to their work. Share your knowledge and together follow the continued development of the NEC.
As always, keep safety at the top of your list and ensure you and those around you live to see another day.
Thomas Domitrovich, P.E. is a National Application Engineer with Eaton Corporation in Pittsburgh, Pennsylvania. He has more than 20 years of experience as an Electrical Engineer and is a LEED Accredited Professional. Thomas is active in various trade organizations on various levels with the Independent Electrical Contractors (IEC), International Association of Electrical Inspectors (IAEI), Institute of Electrical and Electronic Engineers (IEEE), National Electrical Manufacturer’s Association (NEMA) and the National Fire Protection Association (NFPA). Thomas is involved with and chairs various committees for NEMA and IEEE and is an Alternate member on NFPA 73. He is very active in the state by state adoption process of NFPA 70 working closely with review committees and other key organizations in this effort.